Air Explorer - Air Explorer is a software to manage all your multiple cloud drives (like Dropbox, Onedrive, Google Drive, Mega, Mediafire, Box, Hidrive, Yandex, Baidu,...) as well as WebDav and FTP connections.
Koofr - Koofr offers safe EU based cloud storage with free storage space for life and options to connect multiple cloud accounts (Dropbox, Google Drive, OneDrive) and your personal storages.
CloudHQ - Integrate Box, Gmail, Salesforce, Google Drive, Dropbox, Basecamp, Evernote, and more.
odrive - odrive aggregates all cloud storage. Access, sync, share, and encrypt everything in one place. Integrations to 20+ storage services, desktop sync, Linux support, placeholder files, zero-knowledge-encryption, web client, advanced sharing, and more!
ifttt - IFTTT puts the internet to work for you. Create simple connections between the products you use every day.
WebDrive - WebDrive File Access Client allows you to open and edit server-based files without the additional step of downloading the file.